Construction Tips: Hanging Slots !!!

ram3n · Post by **ram3n** » Sun Jul 13, 2003 11:20 am

I'm in the process building a slot resonator, and I just finished cutting, sanding and staining. Now I need to actually put the slots on the framed wall. I've already insulated and covered the wall with a black cloth, and the wall is air tight.

In my design, I have a column of 1x8s, then a column of 1x6s, then another column of 1x8s each with a 3/4" gap between them. What is the best way to get the edge of the slots to line up vertically. Should I use a plumb/chalk line to make sure they line up. I have levels and squares and such and I have built many things in the past, I'm just trying to get some advice on the BEST and most EFFICIENT way to do this.

I hope it's clear what I'm asking. If not, just ask me questions.

Also, I was planning to rent a finish nail gun to do the job... please advise on nail size and such.

THANKS in advance.

knightfly · Post by **knightfly** » Sun Jul 13, 2003 5:43 pm

Greg, am I right that you're running the 1x's horizontal?

Are you doing something like each stud cavity a different spacing?

If you're talking about a vertical gap between columns of 1 by's, one way to do it would be to use a plumb bob to make sure that the wall studs are plumb, and if so you could put just one slat on the frame permanently at the bottom and one (temporarily, or clamped if possible) at the top - then, you could either stretch a chalk line between the two boards and butt each intermediate slat up to the chalk line.

Another way would be if you have a long enough straight 1x to use as a guide. You would still mount a slat at bottom and top for guides, but since 1x lumber is really 3/4" it would give you just the gap you need.

As to fasteners, when it comes to things in a studio I'm not really in favor of nails, and especially of nail guns. It can be difficult to get spacing right, and nail guns tend to not "pull in" a board nearly as well as a hammer because they shoot the nail so fast that the board doesn't have time to overcome its inertia and "snug up" against the other board. I prefer small, countersunk screws for anything that may vibrate.

That being said, if you still want to use a nail gun you need at least 1" longer nails than the boards you intend to attach - 2" nails would be perfect for 3/4" slats. I'd put a light bead of silicone caulk down under each slat end when fastening, just to avoid any possibility of rattles in the case of uneven mating surfaces or a slight twist in any of the boards.

I would put the first nail in each end of each slat as straight in as possible, to fix the X-Y position of the slat - then, toenail the rest of the nails alternately for best strength.

What width slots are you planning for each section? The narrower the slots, the more critical the spacing if you're targeting specific frequencies. If that's the case, one way to get consistent spacing of slats is to find shims of the right thickness, and put them between boards while fastening them to the frames. Even if you're not trying for a specific frequency, they will look better if the gaps are as consistent as you can get them.

I hope that helped some - nails will actually work OK, I'm just overly anal about these things... Steve

Michael Jones · Post by **Michael Jones** » Sun Jul 13, 2003 11:46 pm

I would set the first one at floor level. Use a 4' carpenter's level to make sure its level. Then use 3/4" spacers on top of the first slat to set the second. Continue this process until you reach the top.
Use the level every... say 3rd slat to check.

Here's another tip:
If you have the slat set level with your carpenter's level, turn the level 180 degrees, and check it again. If its off, you have a bad carpenter's level.

knightfly · Post by **knightfly** » Mon Jul 14, 2003 4:06 am

"If its off, you have a bad carpenter's level. " - or a gimpy eye :=) Good tip Michael - that happens more than people think it would.

"Then use 3/4" spacers on top of the first slat to set the second. Continue this process until you reach the top. " - You got sucked in by Greg's statement the same way I did at first. :=)

If you run the #'s thru the Helmholz calculator on the SAE site though, you'll see that 3/4" x 7.5" slats separated by 3/4" over a 3.5" gap (my assumption, not mentioned) would give you a center freq of around 550 hZ - doesn't seem like a good frequency for a slot when you could just use plain ole 703.

Greg, can you clarify or verify this for us so we're all on the same page??? Thanks... Steve

ram3n · Post by **ram3n** » Mon Jul 14, 2003 6:16 am

I'll try to answer everyone's question as best I can.

Knightfly:
"Greg, am I right that you're running the 1x's horizontal?"
--- Yes

And I am talking about a 3/4" vertical gap between a column of 1x, not horizontal gaps of 3/4"s. My goal is to make a wideband low mid frequency absorber, so my horizontal slot spacing is going to vary: 1/8", 1/4", and a 1/2". Using the calculator, I will getting down into the lower to mid 100 Hz range up to about 400Hz. I am going to have three columns. The two outer columns are going to be 1x8s 30" long (horizontally). The center column is 1x6s 48" long. My wall is 109.5" long. That leaves me with 1.5" left over, which is where the 2 3/4" veritical gaps come from.

Regarding fasteners, I am going to use screws (that's what I've always used on other projects), not nails. WHAT SIZE SHOULD I USE?

I'm also going to build some spacers so the spacing is consistent so I can target my desired fequencies. Knightfly, I am also very very anal so all the nit picking advice is welcome !!!

knightfly · Post by **knightfly** » Mon Jul 14, 2003 7:54 am

Glad you like nits, 'cause now that I know what you're REALLY up to, here's a doozy - as far along as you already are, you may want to either back up or re-think -

http://www.homer.com.au/phpBB2/viewtopic.php?t=132

Pay particular attention to Barefoot's comments on individual septums, function of cloth, placement of absorbent...

On screws, you can use deck screws (they're long and skinny), #10, 1-1/2 to 2" should work fine with screws. You'll need to use one of those all-in-one pilot bits, and if you're going to plug the screw holes with dowels (for that "pegged construction look) make sure your bit is the right diameter for the dowels. If you're doing that, you won't need quite as long screws. There is a newer deck screw out, forget the name - each box comes with its own bit - looks like a combination of square drive and phillips. Almost impossible to strip the heads, unlike phillips...

If any of your wall framing is really old, be sure to drill deep enough to NOT be driving screws into un-drilled wood - some of the old framing I've run into makes concrete look like acoustic foam. Couldn't even drive a nail into it with a hammer, kept bending. Even a Senco framing nailer had a hard time with anything over a 10 penny... Steve

ram3n · Post by **ram3n** » Mon Jul 14, 2003 2:12 pm

That thread is a doozy, but some damn good info on the resonators !!!

It seems that my resonator will lean towards to mid to upper mid more than the lower mids, especially since I'm lacking the inner perpendicular partitions. Good thing that I always keep my off cuts from everything I do. I have a crapload of offcuts that I think I can get this done with (so I don't have to fork out more money).

I need a little bit of clarification on the cloth though. If I understand correctly, a heavier cloth can increase the bandwidth? Also he mentioned something that anything used to dampen will increase the resonant frequency... can you expand upon this. Because modifying the cloth is no big deal to me, and can be done rather easily.

Well I'm going to think about what mods I feel are necessary... thanks for the info and I'll keep you updated (and I'll be asking more questions I'm sure).

knightfly · Post by **knightfly** » Mon Jul 14, 2003 2:48 pm

"I need a little bit of clarification on the cloth though. If I understand correctly, a heavier cloth can increase the bandwidth? Also he mentioned something that anything used to dampen will increase the resonant frequency... can you expand upon this. " -

Actually, I've been meaning to ask Thomas about part of this and haven't gotten to it yet.

You'll note that he said "shifting it to a slightly higher frequency." - First, I would intuitively disagree with the direction, and agree with the word "slightly" - as in, ignore it, the variances you introduce in building it are more than the effect.

My thoughts (not backed by anything but intuition, beware) are that, if you equate the cloth restriction to a resistor and the volume of the cavity to a capacitor, then you have a "tank" circuit and increasing the resistance should DECREASE the frequency. Since I've not tried this in real life, let's treat it with the respect it doesn't deserve; maybe now that I've gotten around to voicing it, Thomas can 'splain me why I'm outa my mind (again)

Hey, Thomas, you listening Bro?

Let's hope that got his attention, he likes to argue :=)